Jenni Pippuri

Torque Density of Radial, Axial and Transverse Flux Permanent Magnet Machine Topologies

Torque density of radial, axial and transverse flux machine topologies is investigated. A 10-kW, 200-rpm motor is chosen as a test case. Radial and axial flux motors that fulfill the key specifications of the selected test case are designed employing in-house analytical dimensioning tools and MATLAB genetic multi-objective optimization. Rather simple numerical approach is taken to study the transverse flux motor. A 20-pole-pair radial flux motor is found to outperform its axial and transverse flux counterparts in terms of torque density.

Efficient Parallel 3-D Computation of Electrical Machines With Elmer

After its recent improvements described here, open source finite element software Elmer is shown to be a highly efficient option for electrical machine modeling. The parallelization of computational burden is shown to be a necessity. The methods implemented enable applying fully parallel computation to electrical machine models, including rotation and electrical circuits. Computational experiments performed demonstrate that Elmer can effectively utilize several hundreds of computational cores in parallel, making it an attractive alternative when computational speed is of high importance.

Hybrid city bus design evaluation using system level simulations

Effects of different design parameters on the performance of a hybrid city bus were studied. A system simulation model of the hybrid city bus was developed and used for studying the effects of drive motor torque and vehicle mass on vehicle performance, fuel consumption and stability during regenerative braking. Increasing the maximum torque by 60 % from the nominal value was found to improve the fuel efficiency by 8.3 % when the vehicle was driven on Braunschweig cycle. On the other hand, vehicle stability during regenerative braking was analysed to understand the influence of the braking torque on vehicle stability. This is particularly important when operating at limited traction conditions. In situations where only regenerative braking was applied, the stability was found insufficient.

Finite element analysis for bearingless operation of a multi flux barrier synchronous reluctance motor

Self levitation principle for electrical machines has been a promising research area in the last two decades. Bearingless operation of a motor with two different windings (torque and levitation force windings) requires certain design parameters such as winding space and conductors per slot to be chosen correctly. This paper discusses the design aspects of a bearingless synchronous reluctance motor (SynRM) with multiple flux barriers. This type of machine can be very effective in the smooth torque and levitation force production. A finite element analysis is presented to identify the feasibility and practical challenges for the bearingless operation of a SynRM.

Magnetic bearing as Switched Reluctance Motor - feasibility study for bearingless Switched Reluctance Motor

This paper shows a general review of Switched Reluctance Motors (SRM), reports the conversion of Active Magnetic Bearing (AMB) to SRM and discusses methods to estimate the torque produced in SRM. AMB converted to SRM has been tested on a laboratory scale test rig and its torque production measured. The novelty of this paper is the modified analytical method to estimate fringing flux paths enabling more accurate mathematical model to estimate torque. The reason for careful analysis of the air gap forces is the demand for electromagnetic models of the motor to be used in the motor controller. The ultimate goal of our work is to develop self-bearing (self-levitating bearingless) SRM.

Parallel Performance of Multi-Slice Finite-Element Modeling of Skewed Electrical Machines

The multi-slice method allows approximation of the 3-D phenomena without carrying out a full 3-D analysis, e.g., in skewed radial flux electrical machines. The idea is to divide a 3-D machine into several 2-D finite-element models along the axis, connected by electrical circuits. Here we show how the multi-slice method is perfect for parallel computation; the computation efficiency is close to that of 2-D models in modern parallel hardware. The results are shown to agree with 3-D computation and experimental results.

Design of a Permanent Magnet Synchronous Generator Using Interactive Multiobjective Optimization

We consider an analytical model of a permanent magnet synchronous generator (PMSG) and formulate a mixed-integer constrained multiobjective optimization problem with six objective functions. We demonstrate the usefulness of solving such a problem by applying an interactive multiobjective optimization method called NIMBUS. In the NIMBUS method, a decision is iteratively involved in the optimization process and directs the solution process in order to find the most preferred Pareto optimal solution for the problem. We also employ a commonly used noninteractive evolutionary multiobjective optimization method called NSGA-II to generate a set of solutions that approximate the Pareto set and demonstrate the advantages of using an interactive method. This study is the first one to consider an interactive approach for the design of a PMSG. Thus, we promote the further usage of interactive multiobjective optimization methods in the design. Further, we see that these methods could also be very useful in the teaching of electrical machines.

Parallel performance of multi-slice method for skewed electrical machines

Multi-slice methods allow us to approximate the 3D phenomena without carrying out a full 3D analysis, e.g. in skewed radial flux electrical machines. The idea is to divide a 3D machine into several 2D FEM models, only connected by electrical circuits. Here we show how the multi-slice method is perfect for parallel computation; the computation efficiency is close to that of 2D models in modern parallel hardware. The results are shown to match with 3D computation and experimental results.